The cerebrospinal fluid: current concepts of its formation.

Until recently it has been generally accepted that the choroid plexuses are the major source of the cerebrospinal fluid (CSF). However, data now indicate that significant contributions to the CSF are made at extrachoroidal sites. CSF production studies and 24Na transport studies in normal and plexectomized rhesus monkeys supportive of substantial extrachoroidal CSF formation will be presented. Although the exact mechanisms of CSF formation remain to be defined, ultrafiltration is probably involved to a considerable extent. Data indicative of a lymphatic-like role for the CSF will be considered.